Method for producing a cap band for discharge lamps

ABSTRACT

The invention relates to a method for producing a cap band for discharge lamps, in which a substrate band (1) is coated with at least one material to be introduced into the discharge lamp, in particular a mercury alloy (2) and/or getter material (3). 
     According to the invention, a portion (5) of the substrate band (1) is severed in a direction transversely to the longitudinal direction of the substrate band (1) to form the cap band for the discharge lamp, so that the cap band, or portion, is coated over its entire width (BT) with the at least one material.

FIELD OF THE INVENTION

The invention relates to a method to produce a cap band for dischargelamps in which a substrate band is coated with a material to beintroduced into a discharge lamp, especially a mercury alloy and/or agetter material; and to a cap band made by the method.

BACKGROUND

Published, Unexamined Japanese patent application 6-96728, discloses alow-pressure mercury vapor discharge lamp. This discharge lamp has ametal ring cap, which comprises two metal ring portions, in which oneportion has a mercury-dispensing function while the other metal portionhas no such function. The first of these metal portions comprises anickel-coated iron substrate and a mercury alloy, which comprises amercury-titanium alloy powder applied to the substrate.

The mercury alloy is located on one side, the inside of the ringportion, while getter is located on the other side, the outside of thering portion. The amount of mercury to be introduced into the dischargelamp is determined by varying the length of the first portion. That is,if the amount of mercury is to be increased, the length of the firstmetal portion mentioned above is increased.

The ring cap of the previously known discharge lamp is accordingly notformed in one piece but rather comprises a plurality of components. Thisincreases both the costs of production of the ring cap and the costs ofproduction of the discharge lamp.

THE INVENTION

Briefly, a substrate band, having a width of the length of the entirecap band to be formed, or at least a portion thereof, is coated with atleast one material to be introduced into the discharge lamp, typically amercury alloy and/or a getter material. This base or substrate band issevered transversely to its longitudinal direction, to then form the capband, or a portion thereof, for example in combination with an uncoatedcap band strip.

According to the invention, this object is attained by a

The invention has the advantage that from a predetermined length of capband produced by the method of the invention, many portions can be made,and each portion can be processed, e.g. by cutting in a simple way, inparticular to make a one-piece ring cap.

As an example, the width of the substrate band used in the method of theinvention is approximately 12 to 55 mm. If one assumes that for a ringcap a 5-millimeter-wide cap band should be provided, then from onerunning meter of, for example, 42 mm width, of substrate band, 200 capbands can be made by the method of the invention; that is, 199 cuts arerequired. In the prior art, in which a substrate band has a width of 5to 7 mm, only 23 cap bands can be made from 1 meter of substrate toprovide caps with full ring cap circumference of 42 mm.

The application of getter and mercury alloy is multiple times moreexpensive than the material itself. If according to the inventioncutting is done crosswise to the application of material, and moreovercoating is done on one side, then the production speed for one portion(cap band) is multiple times greater (depending on the width BT, FIGS.3, 4), for the same machine speed.

In a further advantageous embodiment of the method of the invention, thecap band is produced by coating the substrate band on one side with theat least one material to be introduced into the discharge lamp, and inparticular with two materials namely with a mercury alloy and getter.This has the advantage, among others, that the coating of the twomaterials on the substrate band can be done simultaneously.

DRAWINGS

The invention will now be described in conjunction with the drawing.

Shown are in:

FIG. 1, a ring cap for a discharge lamp of the prior art;

FIG. 2, a cap band of the prior art;

FIG. 3A, a sectional view of a first embodiment of a cap band, producedby the method of the invention, coated on both sides;

FIG. 3B, a top view of FIG. 3A;

FIG. 4A, a sectional view of a second embodiment of a cap band, producedby the method of the invention, coated on one side;

FIG. 4B, a top view of FIG. 4A; and

FIGS. 5 and 6, two exemplary embodiments of a ring cap produced from acap band according to the invention.

DETAILED DESCRIPTION

The ring cap shown in FIG. 1 for a discharge lamp comprises a two-pieceoval ring 30, which comprises a first metal piece 31 and a second metalpiece 32. The first metal piece may be formed by a cap band, which isshown in FIG. 2.

In FIG. 3, an exemplary embodiment of a cap band produced by the methodof the invention is shown. The width BB of a substrate band 1 isselected such that it is equal to the circumference of the respectivering cap of the discharge lamp. The substrate band 1, that is, a metalband, which has the length LB, is coated with at least one material tobe introduced, particularly by heating, into the discharge lamp.Preferably, the substrate band 1, which for instance comprisesnickel-coated sheet iron, is coated with a mercury alloy 2 and/or gettermaterial 3, for instance by rolling. The coating does not extend overthe entire width of the substrate band, but leaves uncoated margins 6.

The cap band 4 produced by the method of the invention may be formed byone-sided or two-sided coating of the substrate band. Examples for theseembodiments of the cap band are shown in FIGS. 3A, 3B, 4A and 4B. FIG.3A shows a cap band in which the substrate band 1 is coated on one sidewith getter material 3 and on the other side with a mercury alloy 2. Aportion 5 that forms the cap band 4 for a discharge lamp is severed fromthe substrate band 1 transversely to its longitudinal direction LB(which as a rule is the direction in which the material is applied).When the portion 5 is installed in a lamp, the cap band will havecoating over its entire width BT with at least one material, see FIGS. 5and 6, and compare with FIG. 1.

The cap band produced by the method of the invention has a length LT inthe range of approximately 12 to 55 mm, for instance. The respectivelength LT, as already noted, is equivalent to the circumference of therespective ring cap of the discharge lamp for instance, 48 mm for a T8low-pressure mercury vapor discharge lamp with a diameter of 8/8 inches.

The cap band shown in FIGS. 4A and 4B, produced by the method of theinvention, is coated on one side. Getter material and the mercury alloyare accordingly located on the same side of the cap band. The cap bandshown in FIG. 4A has a width of 44 mm.

In FIGS. 3A and 4A, a portion 5 that is 5 mm in width is shown on theright-hand side of the substrate band 4 of FIGS. 3B and 4B of each.According to the invention, from the running substrate band, forinstance as it is shown in FIGS. 3A and 4A, portions 5 are cut, eachhaving a width BT of 5 mm (length LT of the portion 5=width BB of thesubstrate band 1=circumference of the ring cap=44 mm). By thedetermination of the width BT of the portion, in the present case 5 mm,the quantity of material (mercury alloy and/or getter) to be introducedby heating into the discharge lamp is determined. On the other hand, thequantity of material to be applied per unit of length of substrate bandis determined width BT of the cap band being as strong as possible viewto a possible fixed width BT of the cap band.

A cap band produced by the method of the invention as described is usedto produce a discharge lamp, in such a way that it is introduced intothe discharge lamp and secured therein.

According to the invention, this cap band has a length that is equal tothe circumference of a ring cap of the discharge lamp (such as 44 mm).The width of the portion or of the cap band is 5 mm, for instance, andthis width is chosen as a function of the material to be introduced intothe discharge lamp. Accordingly, the substrate band is coated in such away that the quantity of material or materials intended for thedischarge lamp is applied over a substrate band portion that is intendedfor a discharge lamp and has a predetermined width BT, for instance of 5to 7 mm.

The portion is optionally curved into the specified shape, introducedinto the discharge lamp, and secured there.

A discharge lamp according to the invention thus has a cap band 4 of thekind described above and claimed.

The ring cap shown in FIG. 5 comprises solely a cap band 4 according tothe invention, which is welded on its ends, while the ring cap 60 shownin FIG. 6 comprises one cap band according to the invention and onefurther band 10, the portion 64 and the further band being welded to oneanother.

I claim:
 1. A method for producing a cap band for discharge lamps,comprising the steps ofproviding a substrate band (1) coated withmaterial to be introduced into the discharge lamp, optionally at leastone of: a mercury alloy (2) and a getter material (3), said methodcomprising the steps of severing, transversely to the longitudinaldirection (LB) of the substrate band (1), a portion (5) of the substrateband, said portion forming the cap band (4, 60) or a portion (64) of thecap band, which is coated over its entire width (BT) with the material.2. The method of claim 1, characterized in that the substrate band (1)has a width (BB) that is equal to the circumference of a ring cap of thedischarge lamp.
 3. A method in accordance with claim 1, characterized inthat the cap band is produced by one-sided coating of the substrate band(1) with the material to be introduced into the discharge lamp.
 4. Themethod of claim 1, characterized in that said material comprises atleast one of a mercury alloy and a getter.
 5. The method of claim 1,characterized in that the substrate band (1) has a width (BB) in therange from approximately 12 to 55 mm.
 6. The method of claim 1,characterized in that the severing step comprisessevering the portion(5) of the substrate band (1) forming the cap band (4, 60) to have adimension such that said portion forming said cap, intended for thedischarge lamp, has that quantity of the material or materials appliedwhich is intended or destined for the discharge lamp.
 7. A method forproducing a discharge lamp, utilizing a cap band (4, 60),comprisingcarrying out the method of claim 1; and introducing andsecuring said so-severed portion in the discharge lamp.
 8. A cap bandfor a discharge lamp, wherein the cap band (4, 60) is coated withmaterial to be introduced into the discharge lamp, optionally at leastone of a mercury alloy and a getter material, characterized in thatthecap band (4, 60) or a portion (64) of the cap band (60), severed,transversely to the longitudinal direction of a substrate band, iscoated over its entire width (BT) with said material; and wherein saidcap band (4, 60), or at least said portion (64) of the cap band, aremade according to the method of claim
 1. 9. The cap band of claim 8,characterized in that the cap band (4) has a length (LT) which is equalto the circumference of a ring cap of the discharge lamp.
 10. Adischarge lamp having the cap band of claim
 9. 11. The cap band of claim8, characterized in that the cap band (4, 60) is coated on one side withthe material to be introduced into the discharge lamp.
 12. A dischargelamp having the cap band of claim
 11. 13. The cap band of claim 8,characterized in that it is coated with at least one of: a mercury alloy(2) and a getter (3).
 14. A discharge lamp having the cap band of claim13.
 15. The cap band of claim 8, characterized in that it has a length(LT) of approximately 12 to 55 mm.
 16. A discharge lamp having the capband of claim
 15. 17. The cap band of claim 8, characterized in thatwith a full width (BT) of approximately 5 to 7 mm, the cap band has thequantity of the material or materials applied thereon intended ordestined for a discharge lamp.
 18. A discharge lamp having the cap bandof claim
 17. 19. A discharge lamp having the cap band of claim 8.